The present invention relates to a two-needle sewing machine which drives two needles simultaneously to thereby execute a sewing operation and, in particular, such two-needle sewing machine suitable for use as a belt loop sewing machine which sews a belt loop on a workpiece.
Conventionally, as an example of a two-needle sewing machine, there are proposed various types of belt loop sewing machines each of which is used to sew a plurality of belt loops to be inserted through a belt onto the waist portions of various workpieces (things to be sewn) such as jeans, pants, skirts and the like.
Here, FIGS. 7 and 8 show an example of the above-mentioned conventional belt loop sewing machines, which is disclosed, for example, in U.S. Pat. No. 5,588,384. In particular, the conventional belt loop sewing machine 1 comprises a sewing machine main body 2 serving as sewing means, as well as a belt loop forming device 3 and a belt loop supply device 4 which are respectively added to the sewing machine main body 2.
The sewing machine main body 2 is formed of, for example, a two-needle cycle sewing machine. In the interior portion of a sewing machine arm 6 that is located on the free end side (in FIG. 7, on the left side) thereof, there is disposed a needle rod drive mechanism 21 (FIG. 8) which is connected in such a manner as to be able to move a needle rod 8 up and down in linking with the upper shaft 22 (FIG. 8) of the sewing machine. To the lower end of the needle rod 8, there is fixed a needle stopper 8a, while two parallel arranged needles 7 and 7 are respectively fixed to the needle stopper 8a.
Also, downwardly of the sewing machine arm 6, there is disposed a long and narrow sewing machine bed 5 in such a manner that it extends in parallel to and is opposed to the sewing machine arm 6. On the upper surface of the sewing machine bed 5, there is disposed a needle plate 9 including needle holes 9a through which the needles 7 can be inserted. And, at the vertically moving positions of the needles 7, there are provided a pair of hold feet 10 in such a manner that the hold feet 10 can be pressure contacted with the upper surface of the needle plate 9 due to an elastically energizing force to thereby hold a cloth S between them. The hold feet 10 and 10 are supported by a known cloth hold device (not shown) in such a manner that it can be moved up and down with respect to the needle plate 9.
At the vertically moving positions of the needles 7 in the interior portion of the sewing machine bed 5, there are disposed a pair of known vertical hooks 27a and 27b which respectively include therein bobbins with lower threads wound therearound and cooperate together with the needles 7 in forming stitches. And, the vertical hooks 27a and 27b can be rotated in linking with lower shafts 26a, 26b, 26c, 26d (FIG. 8) which are respectively connected to the above-mentioned upper shaft.
In the belt loop sewing machine 1, generally, an operator works on the free end side of the sewing machine arm 6 and, for the sake of convenience, in FIG. 7, the free end side of the sewing machine arm 6 is expressed as FS, whereas the opposite side thereof is expressed as BS. In one side portion of the fee end side FS of the sewing machine main body 2, there are arranged the above-mentioned belt loop forming device and belt loop supply device 4.
The belt loop forming device 3 not only sends out a long loop material 12 for forming a belt loop along the longitudinal direction of the sewing machine main body 2 toward the FS side thereof by a supply source (not shown) disposed on the BS side of the sewing machine main body 2 but also cuts the loop material 12 into a given length to thereby form a belt loop.
That is, a loop send-out base 13 is disposed almost parallel to the sewing machine bed 5, and a disk-shaped cloth send gear 14, which serves as loop send-out means, with send teeth 15 formed on the outer peripheral surface thereof is disposed on the upper portion of the loop send-out base 13. In operation, the cloth send gear 14 is contacted with the upper surface of the loop material 12, which is shown by an imaginary line in FIG. 7, supplied onto the loop send-out base 13, and, due to the rotation of the cloth send gear 14 when it is driven by a loop send-out motor (not shown), the loop material 12 is sent out by a given amount toward a supply position which is set on the FS side.
Downstream of the loop send-out base 13 in the send direction, i.e. in the direction of an arrow B shown in FIG. 7, of the loop material 12, there is disposed cutting means 16 which is used to cut the loop material 12 into a given length. The cutting means 16 comprises a fixed blade which is fixedly mounted downwardly of the passage of the loop material 12, and a movable blade which is normally situated upwardly of the passage of the loop material 12 and can be moved down by cutting drive means (not shown) such as a cylinder or the like so as to be able cooperate together with the fixed blade in cutting the loop material 12.
Downstream of the cutting means 16 in the send direction, i.e. in the arrow B direction in FIG. 7, of the loop material 12, that is, at the supply position, there are disposed a pair of front and rear loop receiver members 17 which are used to support the cut formed belt loop having a given length, while the loop receiver members 17 are respectively formed in an L-like shape in which the leading end thereof is bent upwardly from below the belt loop. Also, between the two loop receiver members 17, there is interposed a guide rod 19 which is bent downwardly from one end side of the belt loop into an L-like shape. The guide rod 19 is used to hold the position of the loop material 12 sent to the supply position at a given position, while the guide rod 19 is also referred to as a loop move-up rod. That is, since the guide rod 19 moves up the side surface of the loop material 12 to a given position to thereby arrange the loop material 12 in order, when the two ends portions of the belt loop cut to a given length are bent by forks 20, the bent portions are prevented from shifting in position and can be overlapped together completely.
Now, the belt loop supply device 4 not only holds the two ends neighboring portions of the belt loop having a given length held at the supply position by the two loop receiver members 17, but also bends the two ends neighboring portions and then delivers the thus treated belt loop to a sewing position. The belt loop supply device 4 includes a pair of right and left forks 20 which are structured such that, after they hold between them the two ends neighboring portions of the belt loop having a given length held at the supply position by the two loop receiver members 17, they bend the two ends neighboring portions by 180 degrees in a downwardly folding manner, and, after then, they deliver the belt loop to the sewing position. Also, the respective leading end portions 20a of the two forks 20, as shown in FIG. 7, are normally situated at their respective retreat positions which are spaced to the right apart from the supply position, while the leading end portions 20a can be rotated as well as advanced and retreated by fork drive means such as an air cylinder or the like.
According to the conventional belt loop sewing machine having the above-mentioned structure, at first, the loop material 12 is sent out to the supply position from the upper surface of the loop send-out base due to the rotational movement of the cloth send gear 14 and is supported from below by the two loop receiver members 17 and, at the same time, the thus sent-out loop material 12 is moved up and is thereby arranged to one side by the guide rod 19. Next, the two forks 20 are advanced toward the BS direction from the retreat position to the supply position and the leading end portions 20a of the two forks 20 are inserted into the belt loop. After then, the base end portion side of the loop material 12 is cut to a given length by the cutting means 16, thereby forming a belt loop.
Then, the leading end portions 20a of the two forks 20 are rotated to thereby bend the two end portions of the belt loop by 180 degrees in a downwardly folding manner, and the forks 20 and 20 hold the thus treated belt loop between them and deliver the same from the supply position to the sewing position on the sewing S. After then, the cloth hold feet 10 are moved down to thereby hold the sewing S and belt loop on the needle plate 9. Further, after the forks 20 are retreated and are thereby pulled out from the belt loop, for example, the two side folded portions of the belt loop in the longitudinal direction thereof are sewn according to a given sewing pattern using the two needles 7 respectively supported by the needle rod drive means, so that the belt loop can be sewn at a given position of the sewing S.
By the way, preferably, the distance or gap between the two needles 7 supported by the needle rod 8 may be adjusted according to the length of the belt loop. For this purpose, there may be prepared a plurality of needle rods 8 which differ in the gap between the two needles 7 to be mounted thereon, and a desired one of the needle rods 8 may be selected and mounted on the needle rod drive means according to the length of the belt loop.
Or, the needles 7 may be structured such that they can be moved and adjusted in a direction at right angles to the cloth feed direction with respect to the needle stopper 8a.
When the gap between the two needles 7 is set in such a manner to be adjustable according to the length of the belt loop, the gap between the two hooks disposed opposed to the two needles 7 must also be formed in such a manner as to be adjustable.
For this reason, in the conventional belt loop sewing machine, as shown in FIG. 8, the other hook 27b is disposed in such a manner that it can be moved and adjusted in the axial direction thereof with respect to one hook 27a. That is, a crank mechanism 23 is provided in the base end portion of the upper shaft 22 and, by means of the crank mechanism 23, the rotation of the upper shaft 22 is transmitted to a lower base shaft 24 which is disposed within the sewing machine bed 5 and in parallel to the upper shaft 22. Also, a first lower shaft 26a and a second lower shaft 26b are respectively disposed within the sewing machine bed 5 in such a manner that they are spaced from each other in the vertical direction and they are arranged in parallel to the lower base shaft 24; and, the rotation of the lower base shaft 24 is transmitted to the first and second lower shafts 26a and 26b by means of a gear mechanism 25a composed of gears which are respectively provided on the shafts 24, 26a and 26b.
The first vertical hook 27a is fixed to the leading end of the first lower shaft 26a. On the other hand, a third lower shaft 26c is disposed on the same axis as the second lower shaft 26b, and the mutually opposed ends of the second lower shaft 26b and third lower shaft 26c are respectively fixed to a sleeve-shaped joint 28 by screws 29, while they are structured such that they can be integrally moved and adjusted in the axial direction thereof. Upwardly of the third lower shaft 26c, there is disposed a fourth lower shaft 26d which is structured such that the second vertical hook 27b is fixed to one end of the lower shaft 26d in the axial direction thereof, whereas the other end thereof in the axial direction is connected with the third lower shaft 26c through a gear mechanism 25b.
As described above, since the first and second vertical hooks 27a and 27b must be respectively set so that they correspond to the gap between the two needles 7 respectively supported by the needle stopper 8, in the above-mentioned structure, if the screws 29 are loosened to thereby advance or retreat the third lower shaft 26c in the axial direction with respect to the joint 28, then the projecting length of the third lower shaft 26c can be adjusted. Also, the fourth lower shaft 26d is disposed in such a manner that it can be moved and adjusted in the axial direction integrally with the third lower shaft 26c as the projecting length of the third lower shaft 26c is changed in the axial direction. In more particular, the third and fourth lower shafts 26c and 26d are supported by a casing 5A which is different from the sewing machine bed 5 and the present casing 5A is structured such that it can be moved in the axial direction thereof.
According to the above-mentioned structure, when the gap between the two needles 7 is adjusted according to the length of the belt loop, if the screws 29 of the joint 28 are loosened to thereby adjust the axial-direction positions of the third and fourth lower shafts 26c and 26d so that the second vertical hook 27b can be situated just below the position-changed needle 7, and after then, the screws 29 of the joint 28 are tightened to thereby fix the third lower shaft 26c, then the above-mentioned belt loop sewing operation can be executed.
However, in the above-structured conventional belt loop sewing machine, each time the gap between the two vertical hooks 27a and 27b is adjusted according to the adjustment of the gap between the two needles 7, the screws 29 must be loosened, which makes it troublesome to adjust the distance between the two vertical hooks 27a and 27b.